The present invention relates to a fluorine containing carbon film capable of being used as, e.g., an interlayer dielectric film of a semiconductor device, and a method for depositing the same.
In order to achieve the high integration of a semiconductor device, it has been developed to provide devices, such as the scale down of a pattern and the multilayering of a circuit. As one of such devices, there is a technique for multilayering wirings. In order to provide a multilevel interconnection structure, a number n wiring layer and a number (n+1) wring layer are connected to each other by means of a conductive layer, and a thin-film called an interlayer dielectric film is formed in a region other than the conductive layer.
Typically, the interlayer dielectric film is an SiO2 film. In recent years, in order to accelerate the operation of a device, it has been required to reduce the relative dielectric constant of the interlayer dielectric film, and the material of the interlayer dielectric film has been studied. That is, the relative dielectric constant of an SiO2 film is about 4, and it has been diligently studied to dig up materials having a lower relative dielectric constant than that of the SiO2 film. As one of such materials, it has been studied to put an SiOF film having a relative dielectric constant of 3.5 to practical use. The inventor has taken notice of a fluorine containing carbon film (which will be hereinafter referred to as a xe2x80x9cCF filmxe2x80x9d) having a still lower relative dielectric constant.
Such a CF film is deposited by a plasma thin-film deposition method utilizing, e.g., the electron cyclotron resonance (ECR) produced by the interaction between a microwave and a magnetic field. Referring to FIG. 10, an example of this thin-film deposition will be described. At the same time that a microwave of 2.45 GHz is supplied to a plasma producing chamber 1A via a waveguide 11, a magnetic field of 875 gausses is applied thereto by means of an electromagnetic coil 12 to activate Ar gas, which is a plasma producing gas, to form high-density plasma using the electron cyclotron resonance. By this plasma, thin-film deposition gases, e.g., C4F8 gas and C2H4 gas, which have been introduced into a thin-film deposition chamber 1B, are activated to form active species to deposit a CF film having high adhesion and hardness on a semiconductor wafer (which will be hereinafter referred to as a xe2x80x9cwaferxe2x80x9d) arranged on a mounting table 13.
By the way, FIG. 11 shows a part of a circuit portion formed on a wafer, wherein reference numbers 14 and 15 denote CF films, 16a and 16b denoting conductive layers of tungsten (W), 17 denoting a conductive layer of aluminum (Al), 18 denoting an SiO2 film, into which phosphorus (P) and boron (B) are doped, and 19 denoting an n-type semiconductor region 19.
Thus, the CF film is used as an interlayer dielectric film of an element. The CF film deposited by the above described method has a high leak current to deteriorate the insulation performance between wirings, so that the element is not able to have required characteristics. Therefore, there is a problem in that the yield of the element decreases in mass production.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a CF film, which is able to be used as, e.g., an interlayer dielectric film of a semiconductor device, and which has a low leak current, and a method for depositing the CF film.
According to one aspect of the present invention, a fluorine containing carbon film contains carbon, fluorine and boron. Such a fluorine containing carbon film may be deposited by decomposing a thin-film deposition gas, which contains a compound gas of carbon and fluorine, and boron, and depositing a fluorine containing carbon film on a substrate to be treated, by a chemical vapor deposition.
The fluorine containing carbon film may be deposited by decomposing a thin-film deposition gas, which contains a compound gas of carbon and fluorine, to deposit a fluorine containing carbon film on a substrate to be treated, by a chemical vapor deposition, and thereafter, adding boron to the fluorine containing carbon film. The method for adding boron may be a method for heating the substrate after implanting boron ions into the fluorine containing carbon film deposited on the substrate, or a method for activating a boron containing gas to form a plasma and irradiating the fluorine containing carbon film, which has been deposited on the substrate, with the plasma.
According to the present invention, it is possible to provide a CF film having a small leak current. It is also possible to provide a CF film having a lower relative dielectric constant. Therefore, if this CF film is used as, e.g., an interlayer dielectric film of a semiconductor device, it is possible to surely obtain an element having required characteristics. Since it is required to scale semiconductor devices down and to accelerate the operation of semiconductor devices and since CF films are noticed as effective dielectric films having a lower relative dielectric constant, the method of the present invention is effective in the practical use of CF films as dielectric films.